Removal of metal contaminants from petroleum



United States Patent '0 REMOVAL OF METAL CONTAMINANTS FROM PETROLEUMKevin E. Kavanagh, Douglaston, and Ralph P. Chesluk, Beacon, N. Y.,assignors to The Texas Company, New York, N. Y., a corporation ofDelaware No Drawing. Application June 15, 1953, Serial No. 361,859

7 Claims. (Cl. 196-23) This invention relates to a process for removingmetal contaminants from petroleum. More particularly, the inventioninvolves a process for elfectively reducing the vanadium, nickel andiron contents of petroleum fractions.

Metal contaminants, particularly vanadium, iron and nickel, are presentin almost all crude petroleum in the form of hydrocarbon-solublemetallo-organic complex nitrogen compounds. The concentration of themetal contaminants varies widely with the source of the crude, but isvery small, that is, in the order of parts per million. Because of thevery small concentration of the metal contaminants, their removal fromthe crude petroleum or any fraction thereof is extremely diificult.

Attention has been focused on the necessity of removing metalcontaminants from petroleum by the almost unicracking catalysts, butalso changes the selectivity of the catalysts with the result that moreof the hydrocarbon charge is converted to carbon and to gas. In additionto their harmful action on cracking catalysts when present in crackingcharge, metal contaminants present in petroleum fractions also causepitting and corrosion of turbine blades and fuel oils burners.

Present procedures for removing metal contaminants from petroleum eitherresult in a substantial loss of hydrocarbon or concentrate themetal-containing compounds in a particular fraction. One of the meanspresently used to free cracking charge of metal contaminants involvesdistillation of the crude under conditions which prevent entrainment ofthe high boiling metal-containing nitrogen complexes with the resultthat the metal contaminants concentrate in the heavy residual fractions.This method does not solve the problem of metal contaminants because thedense concentration of metal contaminants in the heavy residualfractions causes pitting and corrosion of the burners utilizing thisfuel.

-The process of this invention provides a simple direct procedure forremoving metal contaminants from the crude petroleum. In accordance withthe process of the invention, crude petroleum or a fraction thereof iscontacted with iodine with the resulting conversion of the solublemetal-containing complexes to hydrocarbon-insoluble compounds which aresimply removed from the hydrocarbon fraction by conventional means ofseparating a solid material from a liquid fraction. Filtration isnormally utilized to effect the separation of hydrocarboninsolublecomplexes resulting from contact With iodine, but it is possible toeifect the separation by centrifugal means or by passage of thehydrocarbon fraction through an adsorbent such as alumina or silica gel.

ent in petroleum. Of the three, vanadium is the major olfender becauseit is normally in higher concentration than nickel and iron and becauseit has a particularly harmful elfect on the life and selectivity ofcracking catalysts.

A major advantage of the process of this invention for removing metalcontaminants from petroleum is that the process effect a decrease inconcentration of the metals rather than concentrating the metalcontaminants in a particular fraction.

Another major advantage of the process of the invention is that there issubstantially no loss of valuable hydrocarbon. The hydrocarbon-insolublemetal-containing compounds are removed from the treated petroleumfraction by filtration. There is no measurable loss of hydrocarbon otherthan handling losses which are insignificant in commercialinstallations.

Iodine alone or iodine in a suitable solvent such as acetic acid isemployed as the treating agent in the process of the invention. Solventsthat may be employed are aliphatic acids such as acetic and propionicacids, aliphatic alcohols such as propyl and ethyl alcohol andhalogenated aliphatic compounds such as carbon tetrachloride,tetracholroethane, etc. Acetic acid is one of the preferred solventsbecause it can be simply removed from the treated hydrocarbon by waterwashing. In commercial operation, it is expected that iodine alone willbe used as the treating agent.

The iodine treating agent should be employed in an amount equivalent to0.5 to 15 Weight per cent of the hydrocarbon to be treated. Thepreferred concentration of treating agents falls in the lower part ofthe prescribed range, that is, between 0.5 and 5 weight per cent of thehydrocarbon.

The process of the invention is normally effected in the liquid phase.Vapor phase operation wherein the hydrocarbon fraction in vapor form iscontacted with iodine vapors is very effective in converting thehydrocarbon-soluble metal-containing organo nitrogen complexes tohydrocarbon-insoluble metal-containing compounds, but such excellentresults are obtained by liquid phase operation, it is normally notnecessary to resort to vapor phase operation.

Contact of iodine with the petroleum fraction can be efiected duringdistillation of the crude petroleum. In such type of contact, therewould be a mixed vaporliquid phase contact of the hydrocarbon withiodine with the resulting conversion of the soluble metal-containingcomplexes into hydrocarbon-insoluble metal-containing compounds. Thehydrocarbon-insoluble metal-containing compounds concentrate in theresidual fractions from which they are removed by filtration.

Liquid phase contact of iodine with the hydrocarbon fraction-isgenerally efiected at a temperature between 100 and 350 F. The processis not critical to the 100 to 350 F. range, but excellent results areobtained within this range; Temperatures'above 350 F. are usually notemployed in liquid phase operation When the process of the invention isemployed as a separate treating operation; the shorter contact timesresulting from high temperature contact do not justifiy the theequipment and energy required for maintaining these temperatures.

Atmospheric pressure is normally used for the process of the inventionsince pressure does not appear to be a critical factor. Sub-atmosphericand super-atmospheric pressures can be employed for the process of theinvention so that removal of metal contaminants by iodine treatment canbe integrated with other processing operations such as vacuumdistillation.

The process of the invention can be applied to crude petroleum or toselected fractions thereof obtained by distillation, solvent refining,propane deasphalting or other means of petroIeum refining. The inventionwill be illustrated by the treatment of a crude, but selected fractionsare similarly treated for the removal of metal contaminants therefrom.Bunker C., lube oil fractions and gas oil cracking stock are examples ofselected fractions most widely used in the process of the invention.

The mechanism by which the soluble metal-containing complexes areconverted to hydrocarbon-insoluble metalcontaining compounds bytreatment with iodine is not understood. it is postulated that metalspresent in petroleum are tied up in complex organic porph compounds insimilar fashion to the manner in which iron is part of the hemoglobinmolecule and magnesium is part of the chlorophyll molecule. Whatever bethe mechanism, contact with iodine converts the soluble metal-cont..ning complex nitrogen compounds into hydrocarboil-insoluble metalandiodine-containing compounds. The process is specific to iodine inasmuchas chlorine and iodide salts such as potassium iodide, sodium iodide andcuprous iodide are ineffective in removing metal contaminants fromhydrocarbon fractions.

The process of the invention is illustrated the following examples whichclearly demonstrate how metal contaminants are simply and effectivelyremoved from petroleum by contact with iodine.

Example I 174 g. of Mara crude, which contained 229 parts per million ofvanadium, parts per million of nickel and 5 parts per million of iron,was mixed with g. of iodine and heated to a temperature of 272 F. Themixture of iodine and Mara crude was heated with stirring at thistemperature for minutes. After cooling the mixture to room temperature,it was filtered. The treated oil, whose recovery was theoretical,analyzed 17 parts per million of vanadium, 1 part per million of nickeland 0.5 part per million of iron.

Example 11 20 g. of iodine was added to 100 cc. of acetic acid and theresulting mixture heated in a steam bath until the iodine was partiallydissolved. 217 g. of Mara crude of the same metal content as the crudeemployed in Example I was combined with the acetic acid-iodine mixtureand the resulting composite agitated in a Waring Blendor for 30 minutes.The composite was then filtered and the filtrate water washed to removeacetic acid. The treated crude whose recovery was substantiallytheoretical contained 9 parts per million of vanadium, 1 part permillion of nickel and 1 part per million of iron.

The foregoing examples demonstrate the efiectiveness of the process ofthe invention in removing vanadium, iron and nickel from petroleum. itis noteworthy that single contact of the petroleum with the treatingagent results in more than a twenty-fold decrease in vanadium content,more than a fifteen-fold decrease in nickel content and more than afive-fold decrease in iron content in Mara crude which has aparticularly high concentration of metal contaminants. The more thantwenty-fold decrease in vanadium concentration is particularlysignificant.

The specificity of the invention was demonstrated by treatment of Maracrude with a mixture of acetic acid and chlorine under conditionssimilar to those described in Example Ii; no significant decrease in thevanadium, nickel and iron contents of the Mara crude was eifected bycontact with the chlorine-acetic acid mixture. In similar fashion,treatment of Mara crude with potassium iodide, sodium iodide and cuprousiodide was ineffective in reducing the concentration of vanadium, nickeland iron in Mara crude.

Obviously, many modifications and variations of the invention, ashereinbefore set forth, may be made without departing from the spiritand scope thereof, and, therefore, only such limitations should beimposed as are in dicated in the appended claims.

We claim:

1. A process for treating a heavy petroleum oil selected from the groupconsisting of crude petroleum, residual fractions thereof, heavy fueloil fractions, lubrieating oil fractions and gas oil fractions, saidheavy petroleum oil containing a contaminating amount of oilsolublemetal compounds selected from the group con sisting of compounds ofvanadium, nickel, iron and mixtures thereof, which comprises contactingsaid heavy petroleum oil with a treating agent consisting essentially ofelemental iodine in non-aqueous form under conditions to convert saidoil-soluble metal compounds to oilinsoluble solid metaiandiodine-containing compounds, and separating said oil-insoluble solidcompounds from the heavy oil to'thereby obtain a treated heavy petroleumoil from which at least the major proportion of said contaminating metalcontent has been removed.

2. A process according to claim 1 in which an acetic acid solution ofiodine is employed as the treating agent.

3. A process according to claim 1 in which contact of said iodine withsaid hydrocarbon oil is effected be tween and 350 F.

4. A process according to claim 1 in which separation of said insolublemetal-containing compounds is effected by filtration.

5. A process according to claim 1 in which the hydro carbon oil iscontacted with 0.5 to 15 weight per cent iodine.

6. A process according to claim 1 in which contact of iodine with ahydrocarbon oil is effected in the liquid phase.

7. A process according to claim 1 in which contact of said hydrocarbonoil with iodine is effected during distillation of a crude petroleumfraction with the resulting concentration of hydrocarbon-insolublemetal-containing compounds in the distillation residue.

Rsierences Qited in the file of this patent UNITED STATES PATENTS

1. A PROCESS FOR TREATING A HEAVY PETROLEUM OIL SELECTED FROM THE GROUPCONSISTING OF CRUDE PETROLEUM, RESIDUAL FRACTIONS THEREOF, HEAVY FUELOIL FRACTIONS, LUBRICATING OIL FRACTIONS AND GAS OIL FRACTIONS, SAIDHEAVY PETROLEUM OIL CONTAINING A CONTAMINATING AMOUNT OF OILSOLUBLEMETAL COMPOUNDS SELECTED FROM THE GROUP CONSISTING OF COMPOUNDS OFVANADIUM, NICKEL, IRON AND MIXTURES THEREOF, WHICH COMPRISES CONTACTINGSAID HEAVY PETROLEUM OIL WITH A TREATING AGENT CONSISTING ESSENTIALLY OFELEMENTAL IODINE IN NON-AQUEOUS FORM UNDER CONDITIONS TO CONVERT SAIDOIL-SOLUBLE METAL COMPOUNDS TO OILINSOLUBLE SOLID METAL- ANDIODINE-CONTAINING COMPOUNDS, AND SEPARATING SAID OIL-INSOLUBLE SOLIDCOMPOUNDS FROM THE HEAVY OIL TO THEREBY OBTAIN A TREATED HEAVY PETROLEUMOIL FROM WHICH AT LEAST THE MAJOR PROPORTION OF SAID CONTAMINATING METALCONTENT HAS BEEN REMOVED.